<%#
 Copyright 2013-2025 the original author or authors from the JHipster project.

 This file is part of the JHipster project, see https://www.jhipster.tech/
 for more information.

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

      https://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
-%>
package <%= packageName %>.security.jwt;

import static org.springframework.http.HttpHeaders.AUTHORIZATION;

import org.springframework.cloud.gateway.filter.GatewayFilter;
import org.springframework.cloud.gateway.filter.factory.AbstractGatewayFilterFactory;
import org.springframework.security.oauth2.jwt.ReactiveJwtDecoder;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;
import org.springframework.web.server.ServerWebExchange;

@Component
public class JWTRelayGatewayFilterFactory extends AbstractGatewayFilterFactory<Object> {

    private static final String BEARER = "Bearer ";

    private ReactiveJwtDecoder jwtDecoder;

    public JWTRelayGatewayFilterFactory(ReactiveJwtDecoder jwtDecoder) {
        this.jwtDecoder = jwtDecoder;
    }

    @Override
    public GatewayFilter apply(Object config) {
        return (exchange, chain) -> {
            String bearerToken = exchange.getRequest().getHeaders().getFirst(AUTHORIZATION);
            if (bearerToken == null) {
                // Allow anonymous requests.
                return chain.filter(exchange);
            }
            String token = this.extractToken(bearerToken);
            return jwtDecoder.decode(token).thenReturn(withBearerAuth(exchange, token)).flatMap(chain::filter);
        };
    }

    private String extractToken(String bearerToken) {
        if (StringUtils.hasText(bearerToken) && bearerToken.length() > 7 && bearerToken.startsWith(BEARER)) {
            return bearerToken.substring(7);
        }
        throw new IllegalArgumentException("Invalid token in Authorization header");
    }

    private ServerWebExchange withBearerAuth(ServerWebExchange exchange, String authorizeToken) {
        return exchange.mutate().request(r -> r.headers(headers -> headers.setBearerAuth(authorizeToken))).build();
    }
}
